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No. TBD Issue Draft SC&A Finding NIOSH Response

1 0019-2 (Site 

Description) 

CLOSED

Enrichment levels 

achieved could be 

higher than 2%.

Although assayed specific activity of U-235 in 

cascade product is consistent with given enrichment 

level, maximum assayed specific activity of U-234 

over 50% higher than default value.

The actual enrichment of uranium at Paducah likely 

varied through the years but has been reported to be from 

about 0.7 % U-235 to about 2.5 to 3% U-235. The 

slightly enriched material was then shipped to 

Portsmouth where it was further enriched to 3-5% (BJC 

2000). A footnote in the previous version of the internal

section of the site profile (Berger 2004) stated that the 

predominant level of the enriched product was 1.5% 

although enrichments of up to 5% were eventually 

performed. This footnote could not be traced to a 

technical reference and was removed in revision 2, dated 

04/04/2007. No documents were identified that support 

an enrichment of up to 5% at Paducah. A nominal value 

of 2% was assumed and provides a conservative result 

for the calculated values listed in Table 5-2 of the 

Internal Dose Site Profile for Paducah in comparison to 

natural uranium, which is assumed in the reference 

material (PACE and the University of Utah 2000: BJC 

2000).

2 0019-2 

CLOSED

Number of workers 

assigned zero dose 

needs to be 

disclosed.

Average recorded doses in Tables 2-2 and 2-3 biased 

low and mean little without knowing numbers of 

workers assigned dose values of zero when 

measured dose was less than MDL.

There is a note at the bottom of Table 2-3 that discloses 

that the large numbers of zero dosimeter readings have 

not been included and thus the average values are 

increased in value. Tables 2-2 and 2-3 are not necessary 

to be maintained in the site profile as they are not 

assigned during dose reconstruction. The tables can be 

removed during the next revision to the Site Description 

as the assignment of coworker dose is addressed in 

ORAUT-OTIB-0031.
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No. TBD Issue Draft SC&A Finding NIOSH Response

3 0019-2 

CLOSED

Need to consider 

operations other 

than gaseous 

diffusion.

No mention of smelting operations in Building C746B or smelting of diffusion barriers during 

cascade improvement and upgrade programs, which 

may have contributed significant dose.

The Site Description is intended as an overview of site 

operations and each Paducah facility is not listed here. 

Other sections of the site profile do mention Building C746B. For instance, Building C-746B is called out in the 

internal section of the site profile which provides 

guidance for dose reconstruction. The description of 

Building C-746B can be added to the Site Description 

during its next revision; however, the performance of 

dose reconstructions will not be impacted.

4 0019-3 

(Occupational 

Medical Dose) 

CLOSED

Fails to adequately 

define and assess

occupational 

medical exposure.

Guidelines referenced for Kathren (2003) need to be 

applied in a more claimant-favorable manner.

(SC&A response June 2010 - Rev. 3 of OTIB-0006 

(Kathren and Shockley 2005) referenced; asbestos exams 

cited for completeness.) 

DCAS additional response - Based on the 1,224 Paducah 

non-compensable claims that have been completed to 

date, no records of PFG exams were found. During dose 

reconstruction, typically annual X-rays are assigned to 

overestimate potential X-ray dose, even though the site 

profile indicates an X-ray frequency of every two to five 

years. When actual X-ray records are provided by the 

site, those records are used for X-ray dose assignment. 

When no records are available, a frequency of X-rays 

every 2 years is assumed after 1985 and every 3 years is 

assumed before 1986. The actual X-ray records indicate 

that the frequency of X-ray exams provided by the site is 

less frequent than every 2-3 years.

5 0019-2,3,4,5,6 

IN ABEYANCE

Contamination 

control and skin and 

extremity dose not 

adequately 

addressed.

Insufficient information provided regarding 

radiological controls in place (or lack thereof) for 

operations that pose potential for exposures. 

Contamination control was significant problem and 

should be examined for relevance to skin and 

extremity dose.

When information is presented that indicates a skin 

contamination may have occurred, an evaluation is 

performed during dose reconstruction on a case-by-case 

basis using claimant records and claimant-favorable 

methods described in project documents. In addition, 

modeling programs such as VARSKIN, Microshield, or 

ATILLA can be used to calculate a skin dose – including 

dose to the extremities. The TBD will be updated to 

include current references that are available to assist with 

the calculation of dose to the skin and extremities. These 
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No. TBD Issue Draft SC&A Finding NIOSH Response

include OCAS-TIBs-0010 and -0013, which provide 

guidance regarding geometric correction factors, and, in 

the case of TIB-0010, methods for calculating extremity 

dose using the results of ATILLA modeling. Also, 

OTIB-0017 will be included as a reference for calculating 

dose to the skin from contamination and hot particle 

exposure scenarios. Further, the use of VARSKIN to 

calculate dose to the skin is discussed in OTIB-0017.

NIOSH ACTION: Review of available references 

regarding the estimation of external dose due to skin 

contamination.

Original response was reworded (see above) to better 

describe the process and documents used to estimate skin 

dose and extremity dose. While these documents have 

existed for a good period of time, they will be referenced 

directly in the TBD to help ensure a clear path for the 

DRist in the assignment of skin and extremity dose.

SC&A Response (June 2011): Agree that NIOSH has reviewed and cited available references and will include them as appropriate in the revised TBD. Recommend 

closure of referencing subissue. However, NIOSH agreed following discussion at the July 6, 2011, Work Group meeting that further review on its part is necessary for 

the broader question of how skin dose is addressed in the context of Tc-99 exposure at all three GDPs. Further elaboration useful regarding chronic vs. episodic, how 

to attribute skin and beta dose without dosimetry, what operations involved likely Tc-99 exposure, and the significance of missed dose from this source, and how 

various tools (OTIB guidelines, models) should be applied by dose reconstructors. The Work Group decided to hold this subissue, in the context of potential Tc-99 

exposure, in abeyance. 

Updated DCAS Response (June 2012): A procedure, ORAUT-RPRT-0059, “External Exposure to Technetium-99 at the Gaseous Diffusion Plants” dated 02/07/12

has been written and is being submitted to the GDP Work Group. The procedure provides guidance for the assignment of shallow external dose from Tc-99.

SC&A Response (August 2012): Agree that NIOSH’s response is adequate, per email to the work group on Aug 1, 2012. Recommend closure.

6 0019-4 

(Occupational 

Environmental 

Dose) 

Onsite 

environmental 

exposures based on 

site boundary data.

Basis for applying site boundary monitoring data for 

onsite ambient occupational dose needed to be 

reexamined. No corroborating data provided to 

demonstrate that such measurements are 

representative.

The external environmental doses assigned during dose 

reconstruction are based on the highest monitoring data 

found at the fence line nearest the cylinder yards. In the 

early periods of operation when it was more likely an 

unmonitored employee might have been present in the 

cylinder yards, the dose rates were lower, while in the 
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No. TBD Issue Draft SC&A Finding NIOSH Response

CLOSED

modern era it is unlikely an unmonitored employee 

would spend a significant amount of time in the cylinder 

yards. During dose reconstruction, a maximizing dose of 

0.260 rem/yr is assigned for unmonitored workers whose 

job category and/or work location deem them a nonradiation worker. The assignment of 0.260 mrem/yr is 

higher than assigning a maximizing missed dose based 

on monthly badge exchanges. For internal environmental 

doses, the highest intakes from any of the air sampling 

locations summarized in Tables 4-2 and 4-3 are assigned 

for unmonitored workers whose job descriptions are 

clearly that of a non-radiation worker. These intakes 

include fallout from weapons testing which increase the 

intakes assigned.

The external environmental doses assigned during dose 

reconstruction are based on the highest monitoring data 

found at the fence line nearest the cylinder yards, which 

results in a maximizing dose assignment of 0.260 rem/yr.

TLD data from thirty-three locations in and around 

buildings at Paducah for 1982 and 1984 (Ref # 37840 

and 37842) were reviewed. The TLD results for general 

areas of the site and in buildings, with the exception of 

higher dose rate areas such as the C-746 cylinder yards 

and C-400 pulverizer, were found to be reasonably 

equivalent to the TLD data taken from the twelve air 

sampling stations located at the security fence and at the 

perimeter of the site boundary. In the general areas, the 

data ranged from 14 – 40 mrem/2000 hrs. An outlier in 

the data was results for the C335-A office, which 

indicated TLD results up to 107 mrem/2000 hrs. The 

conclusion is that the environmental dose assessed in the 

site profile is reasonable and claimant favorable even as 

compared to known radiological areas of the site.
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No. TBD Issue Draft SC&A Finding NIOSH Response

7 0019-5 

(Occupational 

Internal Dose)

CLOSED 

Inadequate 

characterization of 

source term for 

internal exposures.

Two references not fully utilized for defining source 

term for internal exposures: PACE/Utah (2000) and 

BJC (2001).

(SC&A response June 2010 - Both references are now 

cited and appropriate information provided.)

8 0019-5, Table 5-2 

CLOSED

Isotopic fractions 

for various 

enrichments not 

properly 

characterized.

Table 5-2 shows some inconsistencies, one being the 

specific activity of U-235 in 93% feed, which 

appears to be a factor of 10 too low.

(SC&A response June 2010 - Former Table 5-2 replaced 

by new Isotopic concentration table, based on specific 

PGDP operations involved.)

9 0019-5, Table 5-4 

CLOSED

Default isotopic 

distribution in Table 

5-4 ignores many 

isotopes associated 

with RU.

Table 5-4 appears to ignore the information 

presented in BJC (2001), Table 2.4-1, which lists 

maximum concentrations of TC-99, Np-237, and 

plutonium for 11 different operations at PGDP.

(SC&A response June 2010 -Table 5-4 deleted (isotopic 

concentrations by operations); BJC reference applied 

otherwise.) 

NIOSH to verify maximum source term values 

reflected.

The maximum source term values from the current 

revision of the internal site profile, Rev. 2 dated 4/4/07 

(now Table 5-2) were compared and found agreeable 

with PACE (Ref ID 10870) Table 7.9 (pg. 88) and 

Bechtel Jacobs Co. (Ref ID 16498) Table 2.4-1 (pp. 30–

31).

SC&A Response (June 2011): Agree that NIOSH has verified that maximum source term values are used in the TBD. At its July 6, 2011 meeting, the Work Group 

closed this issue.

10 0019-5, Table 5-5 Particle size inhaled 

aerosols assumed 

not claimant 

Table 5-5 cites 5μm AMAD for assumed particle 

size of inhaled aerosols, although sizes significantly 

less than that are cited in supporting literature.

(SC&A response June 2010 -Table 5-5 deleted; no 

assumed particle size values provided.)
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No. TBD Issue Draft SC&A Finding NIOSH Response

IN ABEYANCE favorable. NIOSH to verify particle size assumptions used.

No specific particle size study was located for Paducah. 

The 5μm AMAD is used as the default in accordance 

with ORAUT-OTIB-0060 and as recommended in ICRP 

(1994, paragraph 5). 

SC&A Response (June 2011): Questions remain. If 0.5 micron particle size is cited in literature referenced in earlier TBD (see SC&A finding), how is that 

reconciled with statement that “no particle size study was located for Paducah?” The issue is whether any data exist that would obviate use of the default particle size 

of 5 microns. At the Work Group’s July 6, 2011 meeting, NIOSH agreed that it needed to review available references further to ascertain their standing as credible 

bases for applying site specific particle size data, although it believes that the 5 micron ICRP default value would be suitably conservative. The Work Group agreed 

and holds this issue in abeyance awaiting NIOSH’s assessment.

Updated DCAS Response (June 2012): DCAS has reviewed the references as discussed in the SC&A document; Bruner 1960, PACE and Baker 1987 as well as a 

series of other documents that discuss or make reference to particle sizes at Paducah. Upon a review of these documents, DCAS could not substantiate the use of a 

lower particle size smaller than the default assumption of 5 micron AMAD. 

The general policy concerning aerosol AMADs applied for dose reconstructions is to use the ICRP default of 5 μm ICRP (1994, paragraph 5) publication 66 unless 

there is adequate information available to justify the use of another aerosol AMAD. An adequate technical basis would detail the methods used to measure the aerosol 

in the workplace, where and when the measurements were performed, and the operations that were ongoing at the time of the measurements. In our opinion, most 

references on the subject, including the two references cited in the review (Baker and Brunner), don't provide a technical basis that is adequate for the purpose of using 

an aerosol AMAD that is different than the ICRP default of 5 μm. In general, there were only a few mentions of particle sizes above and below 5 μm without any 

information as to where the information came from and without any supporting information to specify if the information was from a legitimate study. The PACE 

report stated “No actual study of particle sizes at PGDP, including locations of measurement, measurement methodologies and results of measurements has been 

located.” In the documents reviewed we also found a few common issues that did not support an official particle study: 

• An AMAD of 1 μm was mentioned in a couple of documents, not because it was measured but because it was the default workplace aerosol recommended by 

the ICRP (ICRP 30) at the time of the reports. That AMAD of 1 μm has been superseded by the current default workplace AMAD of 5 μm ICRP 1994 

(publication 66). 

• An aerosols size in terms of 3.0 -3.5 μm mass median diameter (MMD) was mentioned in a couple of documents. In looking at ICRP 66 (1994) equation 

D.5 in Annex D, an MMD of 3 – 3.5 would be roughly equivalent to an AMAD of 4 -5 AMAD. 

SC&A Response (August 2012): Agree that NIOSH response is adequate, per email to the work group on Aug 1, 2012, and recommend work group closure.
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No. TBD Issue Draft SC&A Finding NIOSH Response

11 0019-5, Table 5-5

CLOSED

List and quantities 

of transuranics 

addressed not 

complete or 

claimant favorable. 

Table 5-5 limits TRUs to Np-237 and Pu-239; 

however, TRU in Hanford recycled tails and other 

sources include Pu-238, Pu-240, and Am-241.

(SC&A response June 2010 -Table 5-5 deleted; more 

comprehensive radionuclide source term provided)

NIOSH to verify maximum source term values reflected 

(combined with #9 above)

The maximum source term values from the current 

revision of the internal site profile, Rev. 2 dated 4/4/07 

were compared and found agreeable with PACE (Ref ID 

10870) Table 7.9 (pg. 88) and Bechtel Jacobs Co. (Ref 

ID 16498) Table 2.4-1 (pp. 30–31).

SC&A Response (June 2011): Agree that NIOSH has verified that the maximum source term values are used. At its July 6, 2011 meeting, the Work Group closed 

this issue.

12 0019-5, Table 5-5

CLOSED

Lung clearance 

types need to be 

clearly defined.

Table 5-5 not clear “absorption type” for each 

radionuclide is consistent with chemical forms, and 

that most claimant-favorable assumption will be 

applied by dose reconstructor.

(SC&A response June 2010 -Table 5-5 deleted.)

13 0019-5, Table 5-6

CLOSED

Intakes based on 

bioassay data need 

to take into 

consideration 

frequency of sample 

collection.

Table 5-6 default frequencies for in-vitro 

measurements at various PGDP facilities not 

claimant favorable, given that intervals between 

measurements could have been as long as 1 year 

versus 4-week interval provided.

The default frequencies for bioassay are not used when 

assessing an individual’s dose – the actual sample dates 

for the specific individual are used). 

14 0019-5, Table 5-7

CLOSED

Minimum detectable 

concentrations 

(MDCs) not clearly 

defined.

In many cases, MDCs cited could not be verified 

through their reference documents.

(SC&A response June 2010 -Additional reference cited; 

more specificity given for reference documents cited.)

15 0019-5 Day of sample 

collection needs to 

be taken into 

consideration when 

deriving intakes 

Practice of offsite collection of samples 24-48 hours 

after leaving the plant, with PDGP employees being 

asked to collect samples after 1 or 2 days off from 

work would lead to lowering of calculated intakes, 

which is not addressed in guidance to dose 

This is a programmatic issue not specific to this site 

profile.

Differing sampling frequencies and criteria is normal and 

understood. Sampling dates are provided with bioassay 
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No. TBD Issue Draft SC&A Finding NIOSH Response

CLOSED based on urinalysis. reconstructors. records which are to be used rather than an assumed 

bioassay date. NIOSH assesses two types of intakes: 

intakes from positive results and missed intakes from 

negative results. Missed intake is assigned based on a 

theoretical assumption of a continuous intake that was 

not detected on the date(s) of sampling; in this situation 

(no detectable intake) additional detail of monitoring 

protocol is not needed because a continuous intake is 

assumed up to the limit of detection, unless other 

information indicates the individual had no potential for 

exposure.

If a positive bioassay result(s) is in the records, the DR 

must consider all available information, including, but 

not limited to, individual records, information provided 

in the TBD, and the actual dates of bioassay collection. 

Thus, an intake based on a positive bioassay is casespecific based on all available data.

NIOSH ACTION: Need to evaluate scope and 

significance of issue at Paducah, and implications to 

coworker model dose estimations.

A review of the sampling frequencies was performed 

with the results below. There is not a significant increase 

in the number of samples obtained on Mondays.

PGDP Urine Samples 

Day of Week through 1977a 1977-1988b Sum Fraction of 

total

Sunday 2923 384 3307 2%

Monday 30013 15507 45520 30%

Tuesday 21750 5944 27694 18%

Wed. 24781 14738 39519 26%

Thursday 13377 6248 19625 13%

Friday 12967 3776 16743 11%

Saturday 1079 193 1272 1%
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No. TBD Issue Draft SC&A Finding NIOSH Response

SC&A Response: SC&A’s June 2011 response indicated that it was not clear how a 30% fraction on Mondays (with 44% the following two days) does not represent 

a “significant increase” in sampling frequency in the context of this issue, and that while it is acknowledged that this issue resolves itself for individual dose 

reconstructions, it is less clear how this is resolved in the coworker model. NIOSH at the July 6, 2011, work group meeting, indicated that while Monday urinanalyses 

does represent an under-estimate, particularly of Type F uranium over a weekend time lag, Tuesday through Friday urinalyses represent an over-estimate and more 

than offsets the Monday influence on the overall distribution of bioassay results providing a claimant favorable outcome. On the basis of NIOSH’s explanation, the 

Work Group closed this issue. 

16 0019-5 

CLOSED

Additional 

significant incidents 

with internal dose 

potential need to be 

discussed.

Significant information useful to dose reconstructors 

is not included, including statements by workers that 

urine specimens were collected within 30 minutes of 

an incident which does not allow time for 

equilibrium to be achieved between inhaled activity 

and concentration in urine. Also, bioassays 

performed not always entered into employee’s dose 

record.

This can be noted in the site profile but incidents are 

typically noted in a worker’s file so the DR would be 

aware that a particular sample was collected shortly after 

a potential intake. This will likely have little impact on 

dose reconstructions. PGDP collected many samples 

from each worker so if a sample were collected only 30 

minutes after an incident, which would be insufficient 

time for transport of the material to urine, the next 

sample could be used for the assessment of the acute 

intake.

SC&A to compare Pace 2001 incident list with Table 5-

8 TBD listing.

NIOSH compared the incident list in the TBD, Table 5-8 

with PACE (pp. 31, 51–52) and BJC (pp. 5–7) and they 

were found to be agreeable. When the TBD is updated, 

the note to Table 5-8 will be changed to reflect that 

additional information may be found in the PACE report 

(Ref ID 10870 and BJC 2000 (Ref ID 16498). 

SC&A Response (June 2011): Agree, although this comparison should be discussed with the Work Group at its next meeting. Otherwise, would recommend closure. 

At its July 6, 2011 meeting, SC&A and NIOSH agreed that its comparison of these references indicated comparability. On this basis, the Work Group closed this 

issue.

17 0019-5 Coworker model for 

applying bioassay 

data to unmonitored 

workers is neither 

scientifically valid 

In the coworker model, workers are not classified by 

their jobs or by the buildings where they performed 

their work, and no validation is provided that there is 

a low probability that any unmonitored worker could 

have a higher exposure than the monitored workers 

Typically unmonitored workers have a lower potential 

for exposure to unconfined radioactive material. 

However, claimant-favorable internal doses are assigned 

based on their jobs and the buildings where they 

performed their work. Coworker doses are statistically 
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No. TBD Issue Draft SC&A Finding NIOSH Response

IN ABEYANCE nor claimant 

favorable.

taken as a group. valid and include a number of overestimating 

assumptions, including the fact that U-234 was selected 

as the isotope that would result in the highest internal 

dose when representing “uranium.” Part of the rationale 

is due to the dose conversion factors for U-234 being 7% 

to 31% larger than those for U-235, U-236 and U-238 

(ICRP 68) as well as other factors.

NIOSH to provide reference for evaluating job title and 

work category in coworker applications.

For internal dose assignment, ORAUT-OTIB-0014 

provides guidance to dose reconstructors on when they 

can assign environmental internal doses rather than 

potential workplace exposures to workers and the 

methodology for assigning such doses. Section 3 

discusses identifying employees for whom environmental 

internal doses are appropriate based on job description, 

work location, monitoring data, etc. Attachment A also 

provides job categories and a general indication of 

potential for exposure. When the TBD is changed, 

ORAUT-OTIB-0014 will be added as a reference.

See also, response to Item 20.

SC&A Response (June 2011): Disagree that OTIB-0014 satisfies the need for site-specific information regarding job categories and/or buildings where workers 

performed work; this OTIB provides general information on how to assign environmental doses vs. workplace doses, with Attachment A providing illustrative 

“examples” of general job categories and their corresponding potential for environmental internal exposures. SC&A agrees that OTIB-0031 Table 2 serves to illustrate 

that the most highly exposed workers were monitored before 1960. At the July 6, 2011 Work Group meeting, NIOSH indicated its agreement that OTIB-014 is not 

adequate for guidance and that OTIB-060 would be more applicable; however, it is clear that more site-specific job categories and work locations would facilitate 

coworker application by dose reconstructors. Based on this discussion, the Work Group decided to hold this issue in abeyance until NIOSH can provide clearer and 

more applicable guidance.

Updated DCAS Response (June 2012): Discussion about assignment of unmonitored dose is in the Internal TBD and additional information is being added to discuss 

the assignment of unmonitored/Coworker dose. The three different type of unmonitored dose are environmental dose, the full distribution coworker dose, and the 95th

percentile intake applied as a constant distribution. In most cases, environmental unmonitored dose or the full distribution of co-worker doses are assigned and provide 

claimant favorable internal dose. However, in certain instances, a worker may be assigned the 95th percentile of a constant distribution. Discussion of when a dose 
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No. TBD Issue Draft SC&A Finding NIOSH Response

reconstructor should consider assigning the 95th percentile is being added to the internal TBD.

SC&A Response (August 2012): Agree with NIOSH approach, per email to the work group on Aug 1, 2012, albeit the work group may want to review the additional 

information once it is added to the TBD. Recommend closure of this item given NIOSH’s commitment to add the appropriate information as noted. 

18 0019-5 

CLOSED

Method of 

converting mass 

concentrations of 

uranium to 24-hour 

excretions of 

activity of uranium 

isotopes is not valid.

Default specific activity provided in the internal 

dosimetry coworker model (Ikenberry 2005) should 

be increased from 0.0389 Bq/μg to 0.0541Bq/μg, 

and the daily excretion rate of urine should be 

updated to reflect the latest ICRP recommendations.

Based on a reasonable enrichment of 2%, 0.0389 

Bq/ug is the correct specific activity. The specific 

activity was calculated using information from Table 5-2 

of the internal section of the site profile. Adding the 

uranium constituents from any column of the table results 

in a specific activity of 1.05 E6 pCi/g or 0.389 Bq/μg. 

The specific activities were taken from the Internal 

Dosimetry Technical Basis Document for Bechtel Jacobs 

Company. Also, see response to issue #1 concerning 2% 

enrichment. The current ICRP models are based on 

Reference Man, ICRP 23. The daily excretion rate from 

that document is used project wide and is not specific just 

to the Paducah site profile.

19 0019-6 

(Occupational 

External Dose) 

CLOSED

Shallow dose from 

beta emitters may 

have been 

underestimated.

The TBD indicates that film badges used to derive 

skin doses from beta emitters employed minimum 

absorber thickness of 80 mg/cm2 between the film 

and the source, but film badges appear to have been 

calibrated with a uranium slab without the absorber.

Also, the calibration factor used ignores the 

contribution of lower energy betas from the shortlived daughters of U-238 and U-235, which would 

have been filtered out by the absorber thickness. 

[This additional issue inadvertently left out of 

original SC&A matrix issue statement.] 

The available evidence [SRDB 13681, 8573, 11985] 

indicates that the entire combination badge (i.e., badge 

with plastic laminated photograph or security credential) 

was exposed during the beta calibration. As a result, the 

decrease in optical density compared to the open window 

dosimeter was correctly considered during the 

calibration. The document authored by Thornton, Davis, 

and Gupton 1961 [SRDB 8573] contains an abundance of 

Combination Badge beta energy response considerations 

and data.

There is incorrect information on Table 6-1 which may 

have led to some confusion regarding two-element film. 

Table 6-1 of the Paducah External TBD will be modified 

to reflect that two-element film (not four-element film) 

was used from 1953 – July 1960.
Paducah Issues Matrix Page 12 of 16 Updated by SC&A – October 8, 2012 

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PADUCAH GASEOUS DIFFUSION PLANT ISSUES MATRIX (October 2012)

SC&A Update - New or edited information appears in red text

No. TBD Issue Draft SC&A Finding NIOSH Response

20 0019-6 

CLOSED

Questionable 

assumptions made 

for assigning skin 

and deep dose for 

unmonitored 

workers prior to 

1960 by means of 

coworker data.

Coworker model assumes that, prior to 1960, 

populations of monitored workers included those 

individuals with the highest exposure potential, an 

assumption that may be questionable given that the 

badging practice at the time was to include all 

worker categories regardless of their potential for 

exposure.

[SC&A response - Appears to be resolved with issuance 

of ORAUT-OTIB-0031 (Merwin 2006)]. 

NIOSH to provide reference for evaluating job title and 

work category in coworker applications (OTIB-0020?), 

and how issue of possible cohort badging prior to 1960 

would influence coworker model.

ORAUT-OTIB-0020, Section 3.0, addresses the topic of 

evaluating job title and work category in order to select 

the proper coworker percentile value (either 50th or 

95th percentile) when using coworker data found in 

ORAUT-OTIB-0031. A reference to OTIB-0020 

currently appears in OTIB-0031 and will be added to the 

TBD.

The below table, “OTIB-0031 Table 2 Figure” illustrates 

that the most highly exposed workers were monitored 

before 1960. This is most notable when looking at the 

plot of median dose – there is an easily observable 

decrease in this value at and after 1960. This decrease is 

also illustrated by the 95th percentile plot. This data trend 

indicates the highly exposed population was monitored 

prior to 1960, and the whole population of likely exposed 

workers was monitored after that date as indicated in 

Section 4.2.1.1 of the PACE report.

SC&A Response (June 2011): Agree that NIOSH’s OTIB-0031, Table 2, serves to illustrate that the most highly exposed workers were monitored before 1960. 

Recommend closure. Following work group discussion on July 6, 2011, the Work Group closed this issue. 

21 0019-6 Assessment of 

neutron exposures

appears to 

underestimate dose.

Based on the TBD, it appears that reliable 

monitoring of neutron exposures did not begin until 

1998, and the coworker model may not adequately 

account for missed neutron dose prior to 1960 

(relying on n/p ratios and review of worker activities 

If an unmonitored worker has radiological exposure 

potential based on their occupation and/or work 

locations, then photon coworker doses will be assigned. 

The n/p ratios are then applied to photon coworker doses 

to determine unmonitored neutron dose. Prior to 1960, 
Paducah Issues Matrix Page 13 of 16 Updated by SC&A – October 8, 2012 

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No. TBD Issue Draft SC&A Finding NIOSH Response

CLOSED during 1960–1998). the photon coworker doses are higher when it was more 

likely that the dose rates in the cylinder yards were lower. 

However using the n/p ratio, the unmonitored neutron 

dose assignment would also be higher prior to 1960.

22s 0019-3

CLOSED

Additional factors 

that contribute to 

uncertainties.

The TBD does not consider dose impacts due to 

less-than-optimal use of technology and how that 

can contribute to uncertainties between units.

ACTION: NIOSH will consult with medical x-ray staff 

resource and provide response.

Doses in the Paducah TBD for 1975 and later are based 

on documented facility-specific technique factors and 

standard x-ray machine output tables (NCRP 102). 

Technique factors (machine settings of kVp, mA, and 

time) must be specifically designed to be used with a 

given film speed, intensifying screen speed, development 

process, and other technological factors. Therefore, if 

technique factors for a given machine are known, or can 

be reasonably assumed, then detailed knowledge of the 

film/screen combination or other technology is not 

necessary, as the technique factors themselves have been 

designed to produce adequate images given those other 

factors.

Doses for 1974 and earlier are based on conservative 

entrance air kerma values from ORAUT-OTIB 0006, 

which are based on actual measurements in published, 

contemporaneous medical literature. Using entrance air 

kerma values as the starting point for dosimetry obviates 

the need for detailed knowledge of site-specific 

technology, such as film, screens, processing, grids, etc. 

The use of the conservative entrance air kerma values 

from ORAUT-OTIB-0006 is used across the DOE 

complex when site-specific information is not available.

As a result of using site-specific technique factors (post1975) or conservative entrance air kerma values from 

ORAUT-OTIB-0006 for x-ray dosimetry in the Paducah 
Paducah Issues Matrix Page 14 of 16 Updated by SC&A – October 8, 2012 

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PADUCAH GASEOUS DIFFUSION PLANT ISSUES MATRIX (October 2012)

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No. TBD Issue Draft SC&A Finding NIOSH Response

TBD, the need for detailed information about screens, 

grids, film, and bucky systems is not necessary. This 

approach permits dose reconstruction to be performed 

regardless of subjective judgment of whether technology 

actually used was optimal or not.

SC&A Response (June 2011): Agree that the need for more detailed information regarding screens, grids, film, and bucky systems is not necessary if use is made of 

site specific technique factors (post 1975) or conservative entrance air kerma values from ORAUT-OTIB-0006 for x-ray dosimetry in the Paducah TBD. At the July 6, 

2011 work group meeting, NIOSH noted that a more complete discussion along the lines of their response would be included in the next TBD revision. Based on this 

discussion, the Work Group closed this issue.

23s 0019-5

CLOSED

Erroneous equations 

for estimating 24-

hour excretion.

The provided equations for estimating 24-hour 

excretion on the basis of spot urine samples 

incorrectly written.

ACTION: NIOSH will follow up.

The equation was based on NCRP Report 87 to be used

when specific gravity was reported for a sample and 

could be used to derive a urinary excretion rate. The 

urine specific gravity was never used by NIOSH during 

dose reconstruction for Paducah claims and was 

subsequently deleted from the Internal TBD. There are 

no tools used during dose reconstruction that use the 

erroneous equation.

SC&A Response (June 2011): Agree that the explanation satisfies the substance of the concern, but a commitment to delete or change this equation (and notice the 

error to DRs) is warranted. At its July 6, 2011 meeting, the Work Group closed this issue. 

24s 0019-5

IN ABEYANCE

Use of unverified 

bioassay data.

The database for internal dose data (1952–1976) was 

not verified by DOE for completeness and accuracy,

and it is not clear if NIOSH has done so.

ACTION: NIOSH will review pedigree for database 

and determine if it has been verified and validated 

(V&V).

There appears to have been little V&V on the early (pre1977) bioassay database. Individual hard copy records 

are available in the claimant (NOCTS) files so although it 

would be an extensive effort, verification could be 

performed.

SC&A Response (June 2011): Issue persists. How can NIOSH (and the Board) establish its confidence regarding the completeness and integrity of the database 

without some degree of validation? This should be discussed at the next Work Group meeting with an eye toward some reasonable course of action (e.g., limited data 

sampling). At the July 6, 2011 work group meeting, NIOSH agreed to the need for some sampling means to validate data integrity of the electronic database provided 
Paducah Issues Matrix Page 15 of 16 Updated by SC&A – October 8, 2012 

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No. TBD Issue Draft SC&A Finding NIOSH Response

by DOE (which had not completed V&V). The Work Group decided to hold this issue in abeyance awaiting NIOSH’s assessment.

Updated DCAS Response (June 2012): A V&V effort was completed by performing limited sampling of two of the plant databases. A white paper titled,

“Comparison of Paducah Gaseous Diffusion Plant Hardcopy Bioassay Records to Two Plant Databases” dated 03/12/12 describes the analyses that were performed, 

The evaluation looked at 614 separate lines of data which consisted mostly of a comparison of handwritten logbooks bioassay records against the database used for 

generating the coworker database. Of the 614 lines evaluated, there were 30 errors that could affect the Paducah uranium bioassay coworker study. These 30 errors 

would represent an error rate of less than 5% and consisted of four incorrect dates, two incorrect bioassay results, and twenty four data entries that were found in the 

logbook but not in the database used to generate the co-worker data. 

Considering the large volume of data evaluated in compiling the coworker study (approximately 159,641 lines of data), a very small percentage of sample dates and 

urinalysis results errors, and the omission of a small percentage of line entries, there would likely be little to no effect on the coworker intakes calculated from the data. 

SC&A Response (August 2012): SC&A agrees with NIOSH’s sampling approach and conclusions regarding data validity, per email to the work group on Aug 1, 

2012. Recommends closure by the work group. 

25s 0019-5

CLOSED

Incorrect selection 

of distinct time 

periods.

Not clear why two time periods used in assessing 

chronic intake period when data suggest three 

distinct periods.

ACTION: NIOSH will evaluate how chronic intake 

periods determined and whether, in any case, the 

difference in results is consequential.

SC&A divided the data into three periods instead of two 

distinct periods as NIOSH did. SC&A provided no basis 

why they consider the data to represent three distinct 

periods. Using the mean and standard deviation for the 

first two periods derived by SC&A, the difference 

between the means is 0.116 with a standard deviation of 

0.115. This indicates the difference between the first two 

periods from SC&A as not statistically different from 

zero at the 95% confidence level. By contrast, the 

difference in the means between the first and third 

periods proposed by SC&A is 0.314 with a standard 

deviation of 0.087 which is statistically different than 

zero. This implies that the two periods selected by 

NIOSH provide an appropriate separation of data sets.

SC&A Response (June 2011): Agree that there is little statistical difference between the two time period formats. Recommend closure. At its July 6, 2011 meeting, 

the Work Group closed this issue.
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